Filling systems are complex technical structures comprising a plurality of units for different tasks in a filling process, which tasks must be coordinated to achieve the highest possible productivity, i.e. the filling system should finish the highest possible number of filled or bottled containers per unit of time.
Typically, a filling system includes a plurality of units connected to one another by conveyors on which containers are transported between said units. The units can be bottle fillers, depalletizers, unpacking, cleaning, labeling, printing, packing machines, palletizers, stretch blow molding plants for manufacturing containers of thermoplastic resin, etc. The transport of containers between the units is of major importance. Here, chain conveyors, air conveyors for empty PET bottles, transport stars and devices for feeding and discharging containers are used, for example. Single- and multi-strand transportation routes are being used on the conveyor lines. Since the containers are serially inserted into the units, multi-strand transport streams have to be separated into individual streams. The multi-strand transportation routes serve as buffer zones, to compensate for fluctuations during production. Such filling systems are described, for example, in patent specifications DE 10 2010 021733 A and DE 10 2007 014802 A. A general description of filling systems can also be found in the final report of the research project “Simulationsgestützte Planung und Nutzung von Geträanke- Abfüllanlagen” (project no. 12265-N) which was conducted between Dec. 1, 1999 and Aug. 31, 2001 at the Institute for Materials Handling, Material Flow, Logistics of the Technical University of Munich.
It is one aspect of such a filling system to fill the largest possible number of containers, such as bottles, in the shortest possible time, e.g. with a beverage, while maintaining consistent quality which corresponds at least to the legally prescribed quality standards and hygiene regulations. To ensure this, a system control is required for evaluating data from a plurality of sensors in order to ensure a smooth process, i.e. to detect any malfunctions or disturbances in time and to adapt the system processes correspondingly.
FIG. 1 is an exemplary view of a section of a filling system including two units 1 and 2 which are connected with one another by means of a corresponding conveyor. The section of the conveyor shown in FIG. 1 can be divided into seven portions, wherein the containers 3 in portions B and F are handled by units 1 and 2. For example, unit 1 can be a filling device for containers 3 e.g. for filling bottles with a beverage, and unit 2 can be, for example, a container labeling device for labeling the filled containers. The portions A, C, D, E and G are portions where the containers, such as bottles, are transported. In portion A, bottles are transported to unit 1, e.g. a sterilizing device. In portion C, the containers treated in unit 1 are carried away. The subsequently following portion D serves as a transport buffer where, for example, the single-strand of portion C can be divided into several parallel transport strands or lines. The buffer zone is particularly used to buffer malfunctions of the units located in front and subsequently following. Since the capacity of a filling system is designed with regard to the filler, the buffer is designed in such a manner that sufficient containers are always provided in the buffer to allow the filler to operate continuously, even in case of malfunctions occurring in other components. In portion E, the multi-strand transport route is again separated in buffer portion D and supplied to unit 2. In portion G, the containers treated in unit 2, such as labeled bottles, are carried away and fed to a subsequently following unit, e.g. a printing machine. The transport routes may also include additional feeding means 4 and 6 as well as discharging means 5 and 7. The positioning of both feeding means 4 and 6 and discharging means 5 and 7 according to FIG. 1 is just exemplary and may differ depending on the system's design. For example, the sensors downstream of the units may check, whether the containers are clean or correctly filled and, if a container does not meet the quality standards, it can be removed from the transport stream via the discharging means 5 and 7. Said discharging means may also serve to divert or branch off container streams, for instance when several filling lines of a filling system are arranged in parallel. In case of malfunction of a filling line, e.g. when a container cleaning unit in a line shuts down, a container stream can be diverted, e.g. in order to fill an adjacent buffer. This is done via feeding means 4 and 6. Such parallel filling system has been described, for example, in DE 10 2010 021733 A1. The conveying speeds v1, v2, v3, v4 and v5 in the respective conveyor portions A, C, D, E and G are set in such a manner that a steady state prevails in the production. “Steady state in the production” means that loading and throughput of containers, i.e. also the output of filled containers per unit time, is constant (steady). In case of any malfunction, e.g. when unit 1 (for instance a filling means) stops, or when there is a container jam, for example due to a fallen container, the throughput of the containers or bottles changes at the respective location in the system. Owing to the buffer routes as shown e.g. in FIG. 1 in portion D, any malfunction may temporarily be buffered so that output of filled containers will not be affected for the moment. Hence, it is known from the state of the art that monitoring of the loading of the buffer routes is an effective measure to enable a trouble-free production.
FIG. 1 shows examples for sensor arrangements suitable, according to the state of the art, for monitoring the conveyor belts. Reference number 8 shows a dynamic pressure sensor used to monitor the loading of a buffer. Such a dynamic pressure sensor in the form of jam switches is described, for example, in DE 3 607 858 A or DE 3 616 023 A.
Reference number 9 denotes a non-contact measurement technology known from the prior art for detecting the loading of conveying means, for instance light sensors or light barriers. The use of light sensors in a transport device for feeding articles to a packaging machine is disclosed in utility model DE 20 2008 009166 U1. According to the DE 10 2010 021733 A, a light barrier is disclosed enabling the row of containers being buffered in the transfer route to connect to those containers that are still in the conveyor line without leaving a gap when the filling station was restarted. This type of sensor systems is disadvantageous in that they provide just little information on the state of the transport means and the transported containers and that the future state of the plant cannot or hardly be estimated. For a smooth or trouble-free production, more information is required, particularly for complex systems.
As further known from the state of the art, the sensor technology can be supplemented with image evaluation methods so that the state of the transport means can be detected better.
Reference number 10 of FIG. 1 designates e.g. video cameras for monitoring the conveyor system.
There is, for instance, a commercial camera-based system for the non-contact counting of containers while being transported in a throng of the Werner Nophut GmbH titled “Zählsystem DKAM-28HD”. Said counting system recognizes and counts glass bottles arbitrarily arranged on a conveyor belt. Furthermore, said system is able to recognize whether the bottles are open or closed.
A further development of such a camera-based system for monitoring, controlling and optimizing filling systems for food, in particular beverage bottles, is described in DE 10 2007 014802 A. That method uses an optoelectronic recognition system having at least one electronic camera in conjunction with one downstream computer-based image processing unit. Image processing is used to obtain information on the objects to be seen on the image from the acquired images to determine an operating state of at least one portion of the entire system. Object recognition is done, for example, in accordance with the probing method with subsequently following contour comparison which may be followed by feature recognition. The system may also be used to recognize incorrectly positioned containers, e.g. containers that have topped over. The inflow behavior to the respective systems may also be monitored, e.g. from temporary buffers.
It is a disadvantage of this state of the art that image processing is merely based on the principle of object recognition according to the probing method with subsequently following contour comparison. To do so, each image has to be analyzed individually, each image just reflecting a snapshot of an operating state. To describe the dynamic behavior of the production plant, a single image analysis will not suffice. Further evaluation steps of the individual snapshots which have not been described in detail in the prior art will have to follow. Since each image is first evaluated individually, there is an enormous expenditure of time. It is, therefore, avoided to analyze a plurality of individual images. Hence, the operation will not be intervened until a critical threshold e.g. for the density of the recognized objects at a certain location in the system is reached, i.e. a threshold is either exceeded or gone below.
It is, therefore, desirable to obtain a method for analyzing the dynamic state of a filling system so as to control the system in advance in a better manner. It would also be desirable to have quality features mapped in the filling process.